SYDNEY - Sudden Infant Death Syndrome, or cot death as it is more commonly known, could occur when babies stop breathing because they dream they are back in the womb, an Australian scientist said recently.

George Christos, who has studied the way the brain processes information, said babies who dream they are back in the womb, where they did not have to breathe because their mothers gave them oxygen through the blood, could stop breathing.

"I'm saying if you make the environment of the sleeping child womblike, it may encourage foetal dreams, and that may excite it to revisit foetal breathing pathways," Christos, who teaches at Curtin University of Technology in Perth, told reporters.

Sudden Infant Death Syndrome is the leading cause of death in babies less than a year old. Most SIDS deaths occur between two and four months and are more prevalent in boys.

Christos, who unveiled his SIDS dreaming theory in a recently published book "Memory and Dreams: the Creative Human Mind", said babies' brains are not fully wired up for dreaming until the age of about two months, so they do not run a risk of SIDS in the first month after birth.

His theory was inspired by sleep research experiments at the psychophysiology laboratory at Stanford University in which people said they had stopped breathing while dreaming of being underwater.

Scientists and doctors are baffled as to what causes SIDS.

More than 8,000 infant deaths were blamed on SIDS over the 22 years to 2000, says the National SIDS Council of Australia, or a rate of 0.54 in every 1,000 live births, similar to that in Britain. In the United States, the figure is 2,500 each year.

Studies have shown SIDS could be linked to a variety of factors, ranging from lying the baby down on its stomach and heart irregularities to tobacco use during pregnancy, or using old mattresses that could harbour toxic bacteria.

A campaign to educate people about the benefits of placing babies on their backs has cut the SIDS rate in half.

Warren Guntheroth, paediatrics professor at the University of Washington School of Medicine in Seattle and one of the world's leading SIDS researchers, said the dreaming theory was attractive but not without problems.

Guntheroth said SIDS strikes babies aged two or three months, when dreams of the womb should be getting weaker and diagnostic tests show some babies may not dream at all until six months.

"My concern is that it is difficult to test his hypothesis," he told reporters in an e-mail message. "On the other hand it is highly original and attractive."

Guntheroth said experiments with baby monkeys showed they stopped breathing when cold wet cloths were placed on their faces, showing some animals had inadequate internal alarm systems and stopped breathing when they thought they could not breathe.

He said babies may react the same.

"We concluded that, whether a dream started it or not, that infants lack an adequate internal alarm system and prolonged apnea could be fatal," Guntheroth said.

Australian SIDS workers said Christos' dreaming theory was one of probably 50 current theories on the cause of SIDS. (Agencies via Xinhua)